Quasi-synchronous switching is an important function in substation automation system（SAS）. With the applicationof electronic transformers and the popularization of IEC 61850， the solution for quasi-synchronization in a digitalized substation（DS） has considerably changed. A description is made of the implementing scheme for the function including such modules asthose of the reception of sampled values（SV）， error SV settlement， the re-sampling algorithm， the prediction algorithm ofsynchronizing point， etc. This scheme has fully considered the transmission delay of SVs and improved the traditionalprediction algorithm to meet the application demand in DS. After many laboratory tests and field applications in DSs， thescheme is proved capable of safely and precisely realizing the quasi-synchronization function.